ObjectiveTo study genetic variation and drugresistance of HIV1 after the failure of highly active antiretroviral therapy(HAART) in HIV1/AIDS patients.MethodsFiftyseven patients with HAART failure, including 45 with D4T/3TC/NVP regime，7 with 3TC/AZT/NVP，and 5 with 3TC/TDF/ LPV/r, were enrolled in the study, viral RNA was extracted from plasma, partial HIV1pol gene was amplified by reverse transcription polymerase chain reaction(RTPCR)and nested PCR,and the amplified fragment was sequenced,the phylogenesis of sequences were analyzed by landing the websites http://HIV1db.stanford.edu., and drug resistance variation was analyzed.ResultsPatients with the failure of 3 types of therapeutic regimes all developed drug resistance. Among 57 patients, drugresistant variation in protease inhibitors(PIs) was identified in 7 patients, 1 of whom （1.75%）produced variation in M46IM which resulted in lowlevel resistance to ATV/r,FPV/r,IDV/r,LPV/r and highlevel resistance to NFV; Drugresistant variation in reverse transcriptase inhibitors (RTs) was identified in 32 patients（56.14%）,and 14 （43.75%,14/32）of whom had resistance to 11 kinds of inhibitors(//HIV1db.stanford.edu)，11 (78.57%,11/14) cases were with the regime of D4T/3TC/NVP. Mutation site in patients with secondline drugs(TDF,LPV/r)were less than firstline drugs(D4T,3TC,NVP,AZT). ConclusionDrug resistance variation is the major cause of failure of HIV1 therapy, drug resistance should be monitored during the course of antiHIV therapy.